docs: def decorate(self, fun):
          """Decorate a function for overriding configuration."""
          @wraps(fun)
          def _decorated(*args, **kwargs):
              # Push the config, run the function and pop it afterwards.
              self.push_config()
              try:
                  return fun(*args, **kwargs)
              finally:
                  self.pop_config()
          return _decorated